1. Field of the Invention
The present invention relates to sound absorbing structures for absorbing sounds in sound chambers.
The present application claims priority on Japanese Patent Application No. 2007-265554, the content of which is incorporated herein by reference.
2. Description of the Related Art
Various types of sound absorbing structures having air layers between sound absorbers and walls of chambers (or rooms) have been developed and are disclosed in various documents such as Patent Document 1.                Patent Document 1: Japanese Unexamined Patent Application Publication No. H05-231177        
Patent Document 1 teaches a soundproof device having a sound absorbing structure, wherein a sound absorbing panel, in which square-shaped sound absorbers composed of ceramics are aligned to form irregular surfaces (having recesses and projections), is disposed to form an air layer with a side wall. In this sound absorbing structure, sound propagated toward the wall from the inside of a room is absorbed by sound absorbers while sound transmitted through sound absorbers is attenuated in energy by way of the air layer formed in the backside of sound absorbers; hence, it is possible to efficiently absorb sound.
In order to absorb low-frequency sound by use of sound absorbers composed of “porous” materials such as ceramics as disclosed in Patent Document 1, it is necessary to increase the thickness of an air layer formed between the sound absorbing panel and the wall. However, the space used for purposes other than sound absorbing in a room should be reduced due to the “large” thickness of the air layer. This makes it difficult to form an air layer having an adequate thickness.